Off sched is only for the pressurization panel.

Ok matt.

 

So what is your take on setting the cruise, initial or final ?

 

 

So what is your take on setting the cruise, initial or final ?

 

His take, from what I can see, was that setting the PRES panel is a separate issue from the VNAV disconnect - they're not at all related. So, related to the topic of this thread, it really has no bearing.

Ok kyle, just something that came to mind.

 

Did you do that flight and have to cruise alt set in the FMC?

His take - was just asking what has his SOPs been when setting the cruise alt in the FMC. Initial or final, when you have 2 cruise alt in the FP. nothing to do with press controller.

The pressure controller is automated, I think it takes the cruise altitude set in the FMC as the altitude to pressurise to. If you climb above this it won't know you intended to do that and will warn you.

 

You're much better off just setting the cruise altitude to the altitude you are going to cruise at. I really can't think why you'd do it any other way than this in normal procedures.

Hi james! I only want someone to clarify that this problem i'm having ain't just me. I don't care if its not in the manual or not to set the final cruise first.

 

I just done 4 quick flights set the final cruise alt in the FMC and leveled off at many alt and hit ALT INV.

 

Then i just done 6 random flights infact done some with no flights just set a waypoint 50nm away set FL100 in the FMC leveled off at 6000ft hit ALT INV no problem!

 

BUT when i set my final cruise alt FL200 hit alt inv after select an alt lower than FL200 i get VNAV DISCONNECT,

 

This is a BUG no doubt about that. Can you atleast check this for me because it seems no one else is.

 

Thanks

Why am i getting VNAV DISCONNECT....

 

 

Why am i getting VNAV DISCONNECT....

 

Because you're not operating the aircraft properly, as everyone has been telling you, honestly.

 

Still, I'll check it out in the sim in 10-15 min.

 

 

Why am i getting VNAV DISCONNECT....

 

Yeah, after testing, I'm going with you're not operating the aircraft properly:

 

Test Case #1:

Set FL250 in the FMC CRZ ALT (improperly, as my opt was FL390). Flew up to FL250. Let it settle into the CRZ page of the FMC. Set FL390 in the FMC, selected FL350 in the MCP, hit ALT INTV. No VNAV DISCONNECT. Took it as if it was a regular step climb. NOTE: I did not enter a step value on the CRZ page in this case.

 

Test Case #2:

Set myself back to FL250 (also set in the FMC as the CRZ ALT). Set FL390 in the MCP. Hit ALT INTV. This forced FL390 into the FMC CRZ ALT and began a VNAV climb to FL390. No VNAV DISCONNECT.

 

Test Case #3:

Set myself back to FL250 (also set in the FMC as the CRZ ALT). Set FL390 in the MCP. Hit ALT INTV. This forced FL390 into the FMC CRZ ALT and began a VNAV climb to FL390. No VNAV DISCONNECT. Dropped the MCP value back down to FL350 and hit ALT INTV. This caused a VNAV DISCONNECT and a CHECK ALT TGT on the FMC.

 

...BUT!

 

This isn't how to properly restrict the altitude in the climb. The proper method would have been to simply roll the MCP ALT down to FL350 without pressing ALT INTV.

 

 

 

 

Ops Check Good: Only able to duplicate using improper procedures.

Ok got a vnav disconnect it says in the FMC CHECK ALT TGT

 

If i select an alt in the MCP ALT below 390 i get the disconnect

If i set the alt to 390 and hit alt inv its fine it will climb

Ok, I gotta say that it's been hard to truly understand what exactly you are doing, or more importantly, what you aren't doing because of the poor sentence construction.

 

Before I confuse myself (may be too late...), you are saying that if you roll an altitude into the MCP ALT that is LOWER than FL390, you get a VNAV Disconnect and should also get an FMC message indicating "CHECK ALT TGT." This is a result of two different altitude inputs in the FMC and that in the MCP ALT. That could be because you've set FL250 in the FMC, and 39000 in the MCP ALT. Instead, you should put 39000 into the MCP ALT and also as the cruise level in the FMC, and as you've said, when you do this the aircraft will climb. So it's the process! Before you leave the ground, you put in your final cruise level into the FMC. NOT FL250 or anything else. If the final FL you are trying to reach is FL390, put that into the FMC and leave it alone! As you depart the airport and are climbing, you roll the MCP ALT pursuant to the cleared altitude assignments from the controller. If you are cleared to say FL250, you will likely already have VNAV and LNAV armed and active. So you roll your new cleared altitude assignment of 25000 into the MCP ALT and click the wheel to activate the selection. The aircraft will continue to climb on VNAV up to 25000. Continue doing this until you've been cleared to FL390, your cruising flight level. That is the most preferred and practiced method of managing altitudes.

 

Use the ALT INTV. during climb or descent to delete altitude restrictions in the FMC between your current altitude and the selected MCP altitude.

 

I think the way you are using the ALT INTV mixed with your convoluted practice of FMC programming and altitude management is what is causing this erroneous situation. There are certain processes for certain tasks/goals. Mixing or changing those processes with other features is cumbersome and in the end, will not help you. Do what has been suggested earlier!!!

 

I think what's got him so confused is how he's using the function. Instead of just programming the FMC initially with the final cruise level and then making selections in the MCP ALT to attain certain altitudes due to restrictions and changing the selection as the cleared altitude levels increase on the way to cruise level, he is using ALT INTV, which probably isn't the best method in that situation.

 

Aside from selecting cleared altitude levels on way to cruise level, when would you likely use ALT INTV? Personally, I would use it in this situation: My final cruise level is FL390. I have left KIAD, departure has instructed me to climb to 10,000 and go direct to the GVE VOR. But on my way to GVE, there is an altitude restriction of 8,000 at CSN, a leg in my flight plan before GVE. Instead of the FMC obeying that restriction, I've been cleared up to 10,000 so I would roll that into the MCP ALT and click ALT INT or click the MCP ALT Selector knob to confirm that atitude selection. Now, that is entirely hypothetical and completely unrealistic in terms of the altitude assignments at GVE or CSN, but in theory, that's how I would utilize ALT INTV. To bypass a restriction in the FMC.

 

Im interested in hearing a response from someone who has RW experience in the 738 or comparable and is familiar with the proper/recommended/designed use for ALT INTV, just to gain some perspective.

 

 

Ok, I gotta say that it's been hard to truly understand what exactly you are doing, or more importantly, what you aren't doing because of the poor sentence construction.

I know the posts don't look like it but I believe English is his native language.

Test Case #1:

Set FL250 in the FMC CRZ ALT (improperly, as my opt was FL390). Flew up to FL250. Let it settle into the CRZ page of the FMC. Set FL390 in the FMC, selected FL350 in the MCP, hit ALT INTV. No VNAV DISCONNECT. Took it as if it was a regular step climb. NOTE: I did not enter a step value on the CRZ page in this case.

 

I just done exactly that kyle and got a VNAV DISCONNECT? I know its not a proper procedure, i'm just wanting wanting to find out why i'm getting this disconnect.

A video would help.

Never set one up james. I know it would help alot.

 

 

I know its not a proper procedure, i'm just wanting wanting to find out why i'm getting this disconnect.

The answer to your question is right in your statement. "its not a proper procedure".

Yes i know that but why isn't it in the FCOM? I've searched everywhere for it